Every year a large majority of the vehicles on the road are
caught unprepared for the first ,blast of really cold weather.
Here is a quick 1 list of things to have checked before that first
nasty blast:

Cooling System: If it hasn't been done in a while,
have your cooling system flushed ad put in fresh antifreeze.
And don't forget to have containers, belts, hoses, the pressure
caps and thermostat checked.

Battery & Electrical System: If your battery is
more than a few years old, have it tested. Cold weather is hard
on batteries. Ensure connections are clean and tight. Corroded
or loose connections can give the symptoms of a weak or dead
battery.

Engine: Faulty. wiring, worn spark plugs, a sticking
choke or emission control devices that need attention, can all
lead to hard starting. A diagnostic check-up of the engine can
be a good pre-winter investment.

Oil and Fitter: Dirty oil can give you trouble, in
the winter. Don't forget to check the other fitters on your
vehicle, including fuel, air and transmission filters.